During the drilling and completion of oil and gas wells, various wellbore treating fluids are used for a number of purposes. For example, high viscosity gels are used to create fractures in oil and gas bearing formations to increase production. High viscosity and high density gels are also used to maintain positive hydrostatic pressure in the well while limiting flow of well fluids into earth formations during installation of completion equipment. High viscosity fluids are used to flow sand into wells during gravel packing operations. The high viscosity fluids are normally produced by mixing dry powder and/or granular materials and agents with water at the well site as they are needed for the particular treatment. Systems for metering and mixing the various materials are normally portable, e.g., skid- or truck-mounted, since they are needed for only short periods of time at a well site.
The powder or granular treating material is normally transported to a well site in a commercial or common carrier tank truck. Once the tank truck and mixing system are at the well site, the dry powder material (bulk material) must be transferred or conveyed from the tank truck into a supply tank for metering into a blender as needed. The bulk material is usually transferred from the tank truck pneumatically. More specifically, the bulk material is blown pneumatically from the tank truck into an on-location storage/delivery system (e.g., silo). The storage/delivery system may then deliver the bulk material onto a conveyor or into a hopper, which meters the bulk material through a chute into a blender tub.
The pneumatic conveying process used to deliver bulk material from the tank truck can be a time-consuming process. In addition, some well locations are arranged without a large amount of space to accommodate tank trucks, such that only a limited number of available tank trucks can be positioned to pneumatically fill the storage/delivery system at a given time. Accordingly, the pneumatic conveying process can lead to dead time of equipment usage and relatively high detention costs or demurrage costs associated with the tank trucks, hoses, and related equipment that are on-location during this time.
Furthermore, during the pneumatic conveying process, the bulk material is moved from the tank truck to the storage/delivery system in a turbulent manner, leading to large amounts of dust and noise generation. The air used for conveying the material must be vented from the storage tank and typically carries an undesirable amount of dust with it. Attempts to control dust during the conveying process typically involve the rig up and use of auxiliary equipment, such as a dust collector and duct work, adding cost to the material handling operations.
In addition, traditional material handling systems can have several transfer points between the outlets of multiple storage/delivery systems and a blender. These transfer points often have to be shrouded and ventilated to prevent an undesirable release of dust into the environment. Further, after the dust has been captured using the dust collectors and ventilation systems, additional steps are needed to dispose of the dust.